The objective of this study is to investigate the relationship between DNA adducts and micronuclei in the skin of mice treated with a model polycyclic aromatic hydrocarbon and an aromatic amine (Benzo(a)pyrene BaP, 4-Aminobiphenyl 4-ABP). Both these compounds are significant occupational and environmental pollutants. The specific aims will involve the following: 1. Determine the major DNA adducts formed in mouse skin by topical application of BaP and 4-ABP. This will be accomplished by using 32P- postlabeling techniques. 2. Determine chromosomal damage in mouse skin, as measured by micronuclei frequencies. A monolayer of cells, from exposed and control animals will be grown on cover slips/microscope slides. Approximately 1000 micronuclei will be scored/slide. 3. Establish dose response relationships between DNA adducts and micronuclei frequencies using standard statistical procedures. 4. Evaluate the mechanisms of clastogenicity using cytokinesis-blocked (i.e. binucleated cells. In addition, centromere specific antibodies will be used. This study will be the first to determine the interactions between DNA adducts and micronuclei in the skin, a target organ for many occupational carcinogens. The use of a skin specific carcinogen, BaP, and a carcinogen 4-ABP which does not affect the skin will allow us to investigate whether genetic lesions are formed at lower levels by 4ABP or whether the 4-ABP adducts are formed and subsequently repaired. This design will also allow us to test the hypothesis that it is specific metabolism which is responsible for aromatic amine carcinogenicity.